The  Condensation  of  Carbon 
Tetrachloride  and  Phenol  :Aurin 


A    DISSERTATION 


SUBMITTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIREMENTS 

FOR  THE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY  IN  THE 

UNIVERSITY  OF  MICHIGAN 


By 

Harold  Robert  Snow 


EASTON,  PA. 

HSCHENBACH  PRINTING  COMPANY 
1922 


The  Condensation  of  Carbon 
Tetrachloride  and  Phenol  tAurin 


A    DISSERTATION 


SUBMITTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIREMENTS 

FOR  THE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY  IN  THE 

UNIVERSITY  OF  MICHIGAN 


By 

Harold  Robert  Snow  //v( 


EASTON,  PA. 

ESCHENBACH  PRINTING  COMPANY 
1922 


f\ 


KXCHANGB 


• 


CONTENTS 


I      Introduction 5 

II      The  Mechanism  of  the  Condensation  Reaction 5 

III  The  Separation  of  the  Reaction  Mixture  into  its  Components 6 

IV  The  Relative  Proportion  of  the  Components 8 

V     The  Preparation  of  Diphenyl  Carbonate 8 

VI     The  Preparation  of  Di-£-hydroxybenzophenone 9 

"VII     Aurin 9 

Preparation 9 

Combination  with  Solvents  of  Crystallization 10 

The  Possible  Existence  of  the  Quinoid  Carbinol  of  Aurin 11 

Tri-Acetyl-Aurin 12 

Tri-Acetyl-Aurin  Chloride 12 

Tri-Acetyl-Aurin  Peroxide 12 

Tribenzoyl-Aurin 13 

Tribenzoyl-Aurin  Chloride 13 

Tribenzoyl-Aurin  Peroxide 13 

Decomposition  of  Aurin  by  Air  and  Alkali 14 

Isolation  of  Leuco  Aurin  from  the  Condensation  Product 14 

VIII      o.^'.^'-Trihydroxy-Triphenyl   Carbinol 14 

Isolation  from  the  Condensation  Mixture 14 

Preparation  of  0,/>',£"-Trimethoxy-triphenyl  Carbinol,   by   the   Grignard 

Reaction 14 

0,£',/>"-Trimethoxy-triphenylmethane 15 

IX     />-Hydroxyphenyl-Xanthane 15 

^-Methoxyphenyl-Xanthane 15 

X     ^-Hydroxyphenyl-Fluorone 15 

Isolation  from  the  Condensation  Product 15 

/>-Acetoxyphenyl-Fluorone 15 

£-Acetoxyphenyl-3-Acetoxy-Xanthenol 15 

^-Methoxyphenyl-Fluorone 16 

£-Methoxyphenyl-3-Methoxy-Xanthenol 16 

Synthesis  of  />-Hydroxyphenyl-Fluorone . 16 

Oxidation  by  Air  and  Alkali 16 

XI      The  Oxalic  Acid  Method  for 'the  Preparation  of  Aurin 17 

XII      The  Composition  of  Several  Technical  Samples  of  Aurin 17 

XIII     Summary 18 


578647 


ACKNOWLEDGMENT 

This  investigation  was  undertaken  at  the  suggestion  of  Professor  M. 
Gomberg.  It  is  with  much  pleasure  that  I  acknowledge  my  indebtedness 
to  him  for  his  invaluable  assistance,  and  his  many  words  of  encouragement 
and  advice  throughout  the  whole  of  this  work. 


THE    CONDENSATION    OF    CARBON    TETRACHLORIDE    AND 

PHENOL:  AURIN 

Friedel, l  in  a  note,  states  that  aurin  is  formed  when  carbon  tetrachloride 
is  heated  with  an  excess  of  phenol  and  zinc  chloride.  Heumann2  patented 
a  process  for  producing  aurin  by  heating  under  pressure  carbon  tetrachlor- 
ide and  phenol  with  various  condensing  agents,  such  as  aluminum  chlor- 
ide, stannic  chloride  or  zinc  chloride  and  he  stated  that  without  pressure, 
only  a  trace  of  aurin  is  produced. 

We  have  investigated  this  reaction  and  find  that  Heumann's  assertion 
is  incorrect.  Aurin  is  produced  in  quite  as  good  yield  when  the  condensa- 
tion is  carried  on  at  ordinary  pressure  as  when  in  an  autoclave,  namely, 
about  35%.  We  find  also  that  many  other  products  are  formed  simul- 
taneously with  aurin.  The  successful  isolation  of  certain  intermediate 
products,  together  with  the  identification  of  all  the  final  products,  has 
enabled  us  to  give  an  interpretation  as  to  the  probable  mechanism  of  this 
condensation  reaction. 

We  have  also  studied  the  method  for  making  aurin  which  has  been  com- 
monly used  in  the  past,  namely,  from  phenol,  oxalic  acid  and  sulfuric 
acid,  and  we  find  that  here,  too,  a  mixture  of  various  substances  results, 
and  that  the  technical  product  is  far  from  pure  aurin. 

The  Mechanism  of  the  Condensation  Reaction 

1.  The  first  stage  in  the  reaction  consists  in  the  condensation  of  two 
molecules  of  phenol  with  one  of  carbon  tetrachloride  and  diphenoxy-di- 
chloromethane  (I)  is  thus  formed.3  If  the  requisite  amount  of  water  be 
present  in  the  mixture,  this  dichloride  becomes  hydrolyzed  to  diphenyl 
carbonate  (II),  which  is  stable  and  can  undergo  no  further  change  under 
the  conditions  of  the  experiment.  In  fact,  good  yields  of  diphenyl  carbon- 
ate can  be  obtained  by  this  method. 

1  Friedel,  Bull.  soc.  chim.,  50,  2  (1888). 

2  Heumann,  Friedldnder,  3,  103;  Ger.  pat.,  68,976,  1893. 

3  Gomberg  and  Jickling,  J.  Am.  Chem.  Soc.,  37,  2580  (1915). 


6 

2.  However,  if  the  diphenoxy-dichloride  does  not  become  hydrolyzed 
as  soon  as  formed,  then,  due  to  the  influence  of  the  hydrogen  chloride  pres- 
ent, it  undergoes  an  intramolecular  rearrangement  and  gives  rise  to  di-p- 
hydroxybenzophenone  chloride  (III),  and  to  a  small  amount  of  the  isomeric 
o,-£'-dihydroxy  derivative  (V).     Hydrolysis  of  the  reaction  mixture  at 
this  stage  gives  rise  to  the  two  ketones  (IV)  and  (VI).     This  constitutes  a 
very  excellent  method  for  the  preparation  of  £,£>'-dihydroxybenzophenone. 

3.  If  the  ketones  are  not  the  desired  end-products  of  the  condensation, 
then  hydrolysis  of  the  keto  chlorides  should  be  carefully  avoided.     The  two 
keto  chlorides  described  above  now  condense  further  with  a  third  molecule 
of  phenol,  and  there  are  produced  the  chlorides  of  the  three  possible  tri- 
arylcarbinols :  £,£',£"-trihydroxy-triphenyl  carbinol  (VII),  and  the  two 
isomers  thereof:  o,p',p"  (IX)  and  0,0',  p"  (XI).     Product  VII  is  the  pre- 
cursor of  aurin  (VIII).     Similarly,  Substance  IX  gives  rise  to  the  an- 
hydride of  0,£>/,£"-trihydroxy-triphenyl  carbinol  (X),  while  Compound  XI 
of  course  loses  spontaneously  a  molecule  of  water  from  the  two  o-hydroxyl 
groups,  whereby  a  xanthone  ring  becomes  established  in  the  molecule, 
and  there  is  thus  produced  the  chloride  of  ^-hydroxyphenyl-xanthenol 
(XII). 

4.  Substance  IX,  however,  in  addition  to  its  normal  change  into  X, 
undergoes  in  part  still  another  change.     It,  too,  goes  over  into  a  xanthone 
derivative.     Here,  however,  the  new  ring  is  established  through  the  loss 
not  of  a  molecule  of  water,  but  of  two  atoms  of  hydrogen — the  one  from 
the  o-hydroxyl  group  and  the  second  from  a  CH  group  in  the  ortho  position 
in  one  of  the  other  two  benzene  rings.    There  is  thus  produced  the  un- 
stable compound   (XIII),  which  is  the  precursor  of  ^-hydroxyphenyl- 
fluorone  (XIV).     A  similar  tendency  on  the  part  of  hydroxytriaryl  car- 
binols  to  establish  a  xanthone  ring  within  the  molecule,  through  dehydro- 
genation,  has  been  observed  in  other  cases.4 

5.  The  nascent  hydrogen  which  originates  as  described  in  the  pre- 
ceding paragraph,  reacts  with  the  triarylcarbinol  chlorides  or  the  carbinols 
themselves.     Apparently  under  the  conditions  of  our  experiments  Sub- 
stances VII  and  XII  are  the  two  most  susceptible  to  reduction  and  there 
are   thus   produced   the   two   corresponding  leuco  derivatives,  namely, 
leuco-aurin  (XV)  and  ^-hydroxyphenyl-xanthane  (XVI). 

The  Separation  of  the  Reaction  Mixture  into  its  Components 

Since  the  products  formed,  with  the  exception  of  diphenyl  carbonate, 
contain  phenolic  hydroxyl  groups,  they  possess  acid  properties,  the  de- 
gree of  acidity  depending  upon  the  number  of  hydroxyl  groups  in  the  mole- 
cule, as  well  as  upon  the  configuration  of  the  latter.  Consequently,  the 
constituents  may  be  divided  into  two  main  groups:  (1)  products  soluble 
4  Baeyer,  Ann.,  354,  170  (1907). 


HO 


H°O|!<I>H 


-00 


(XV) 


in  very  dilute  ammonium  hydroxide  solution  (1.5%);  (2)  products  insolu- 
ble in  ammonium  hydroxide  of  that  dilution.  The  basis  for  further  sep- 
aration is  briefly  indicated  in  the  following  outline. 


8 

1.  Products  soluble  in  dil.  ammonium  hydroxide:  (a)  aurin  (insoluble 
in  ether) ;  (b)  di-£-hydroxybenzophenone  (soluble  in  ether,  slightly  soluble 
in  hot  benzene);  (c)  0,£'-dihydroxybenzophenone  (soluble  in  ether,  soluble 
in  hot  benzene). 

2.  Products  insoluble  in  dil.  ammonium  hydroxide:    (d)  ^-hydroxy- 
phenyl-fluorone  (XIV)  (insoluble  in  moist  ether,  in  contradistinction  to  all 
those  below,  all  of  which  are  soluble  in  ether);  (e)  the  o,p',p"-trihydroxy 
compound  (X)  (upon  passing  hydrogen  chloride  into  the  ether  solution  it 
forms  an  insoluble  chloride-hydrochloride,5  and  is  thus  separated  from 
those  mentioned  below,  all  of  which  remain  in  solution);  (f)  leuco-aurin 
(XV)  (soluble,  together  with  a  small  amount  of  unidentified  substances 
(Z),  in  cold  dil.  sodium  hydroxide  solution);    (g)  £-hydroxyphenyl-xan- 
thane  (XVI)  (the  sodium  salt  is  insoluble  in  cold,  but  soluble  in  hot  dil. 
sodium  hydroxide  solution) ;  (h)  diphenyl  carbonate  (not  soluble  in  either 
cold  or  hot  alkali) ;  (i)  (Z)  unidentified  substance  (small  amount) . 

The  Relative  Proportions  of  the  Components 

When  the  relative  proportions  of  carbon  tetrachloride  and  phenol  are 
nearly  those  calculated  on  the  basis  of  the  equation,  one  molecular  equiva- 
lent of  the  former  to  3.5  of  the  latter,  and  when  all  moisture  is  carefully 
excluded,  then  the  amount  of  aurin  is  usually  32%  to  35%  of  that  calculated, 
and  it  constitutes  about  55%  in  weight  of  all  the  condensation  products. 
The  data  following  are  the  averages  of  ten  carefully  conducted  experi- 
ments, using  each  time  154  g.  of  carbon  tetrachloride,  330  g.  of  phenol 
and  50  g.  of  zinc  chloride:  aurin,  90-94  g. ;  ^-hydroxyphenyl-fluorone, 
25  g. ;  0,£>',£//-trihydroxytriphenyl  carbinol,  15  g.;  leuco-aurin,  20  g. ; 
£>-hydroxyphenyl-xan thane,  7  g.;  ketones,  very  small  amount;  diphenyl 
carbonate,  trace. 

Experimental  Part 
The  Preparation  of  Diphenyl  Carbonate 

Diphenyl  carbonate  has  usually  been  prepared  by  methods  which  re- 
quire the  use  of  carbonyl  chloride  and  such  methods  present  obvious  dis- 
advantages. Very  satisfactory  yields  of  this  ester  were  obtained  as  fol- 
lows. 

To  94  g.  (1  mole)  of  phenol  in  a  flask  were  added  10  g.  of  zinc  chloride,  95  g.  (0.55 
mole)  of  carbon  tetrachloride  and  41  g.  (0.5  mole)  of  zinc  oxide  and  the  mixture  was 
heated  under  a  reflux  condenser  at  120°  until  no  further  evolution  of  hydrogen  chloride 
was  noticed.  This  required  about  24  hours.  The  small  amount  of  zinc  chloride  served 
to  start  the  reaction;  thereafter,  the  hydrogen  chloride  produced  in  the  course  of  the 
reaction,  combining  with  the  zinc  oxide,  formed  additional  zinc  chloride  and  this  reac- 
tion also  furnished  the  water  requisite  for  the  hydrolysis  of  the  diphenoxy-dichloro- 
methane  to  the  carbonate.  The  excess  of  carbon  tetrachloride  and  unchanged  phenol 

6  Gomberg  and  Cone,  Ann.,  370,  191  (1909). 


9 

were  removed  by  steam  distillation,  the  distillation  being  continued  until  the  carbonate 
commenced  to  distil.  The  viscous  mass  was  poured  into  a  large  volume  of  water  while 
the  latter  was  vigorously  stirred.  After  the  product  had  been  washed  several  times 
by  decantation,  the  insoluble  residue  was  digested  with  5%  sodium  hydroxide  solution, 
in  order  to  dissolve  the  hydroxybenzophenones  and  the  small  amount  of  dye  present. 
The  carbonate  remained  as  a  white  crystalline  substance,  contaminated  with  a  small 
amount  of  zinc  salts.  It  was  purified  by  recrystallization  from  alcohol;  yield,  45  g.,  or 
50%,  calculated  on  the  basis  of  the  phenol  used.6 

On  passing  sulfur  dioxide  into  the  alkaline  wash  solution,  25  g.  of  crude  dihydroxy- 
benzophenones  was  obtained. 

The  Preparation  of  Di-^-hydroxybenzophenone 

The  procedure  was  very  similar  to  that  used  in  the  preparation  of  di- 
phenyl  carbonate,  except  that  an  increased  amount  of  freshly  molten 
zinc  chloride  (50  g.)  was  used  at  the  start  and  no  zinc  oxide  was  added. 

The  mixture  of  the  ketones  was  isolated  in  the  same  manner  as  indicated  under  the 
preparation  of  diphenyl  carbonate.  The  crude  product  was  then  dissolved  in  dil.  am- 
monium hydroxide,  the  solution  filtered,  warmed  and  treated  with  sulfur  dioxide, 
whereupon  the  ketones  separated  as  almost  colorless  needles;  33  g.  of  the  mixed  ketones 
and  only  a  small  amount  of  carbonate  were  obtained  from  94  g.  of  phenol,  equal  to  a  36% 
yield  based  on  the  phenol  used. 

The  mixture  consists  largely  of  p,p'-dihydroxy  ketone  and  contains  only  a  small 
amount  of  the  isomeric  o,/>'-compound.  The  latter  is  far  more  soluble  in  hot  benzene 
than  the  former,  and  may  thus  be  readily  removed. 

Aurin,  (4,4'-Dihydroxy-diphenylquinomethane  VIII) 
Preparation. — After  many  trials  the  following  procedure  was  finally 
adopted. 

Three  hundred  and  thirty  g.  (3.5  moles)  of  pure  phenol  was  placed  in  a  flask  that 
could  be  connected  to  a  reflux  condenser  by  means  of  a  ground-glass  joint  (if  a  cork 
must  be  used  it  should  be  covered  with  lead  foil).  The  phenol  was  melted  and  into  it 
50  g.  of  molten  zinc  chloride  was  poured  while  the  flask  was  given  a  rotary  motion  so  as 
to  distribute  the  zinc  chloride  in  the  form  of  fine  threads  through  the  solution.  The 
mixture,  carefully  protected  from  moisture,  was  heated  in  an  oil-bath  for  18  hours  at 
135°,  with  the  gradual  addition  of  154  g.  (1  mole)  of  carbon  tetrachloride.  The  viscous 
mass  was  steam-distilled,  in  order  to  remove  the  excess  of  phenol.  It  was  then  poured 
very  slowly  into  2  liters  of  vigorously  stirred  water  containing  60  cc.  of  hydrochloric 
acid.  After  filtering  and  washing  the  material  thoroughly  with  water,  it  was  ex- 
tracted with  1.5%  ammonium  hydroxide.  In  ammonium  hydroxide  of  this  concen- 
tration, aurin  and  the  hydroxybenzophenones  are  dissolved,  while  the  other  products 
(see  scheme  on  p.  8)  are  almost  entirely  insoluble.  The  ammoniacal  filtrate  was 
heated  to  70-80°  and  the  aurin,  with  the  small  amount  of  ketones,  was  precipitated  by 
adding  dil.  acetic  acid  (not  hydrochloric  acid,  see  p.  11)  slowly  and  vigorously  stir- 
ring the  mixture.  The  product  separated  either  as  a  brick-red  powder  or  as  purplish- 
red  crystals,  depending  mainly  upon  the  temperature  of  the  solution  and  the  rate  with 
which  the  acid  was  added.  The  precipitate  was  filtered  and  washed  with  water  con- 
taining a  little  acetic  acid  and  finally  with  water.  In  order  to  remove  any  ketones 

8  Dr.  H.  T.  Clarke  of  the  Eastman  Kodak  Co.  has  been  good  enough  to  test  this 
method  on  a  larger  scale.  From  1200  g.  of  phenol,  heated  at  100-110°  for  15  hours  and 
stirred,  437  g.  of  pure  vacuum-distilled  diphenyl  carbonate  was  obtained. 


10 

present,  the  dry  product  was  first  stirred  with  ether  and  then  allowed  to  stand  overnight, 
whereupon  the  ketones  dissolved.  When  the  ether  is  moist  the  aurin  changes 
to  a  crystalline  product  with  steel-blue  luster,  and  takes  up  ether  of  crystallization. 
The  aurin  is  now  very  pure  and  for  most  purposes  need  not  be  further  purified.  The 
yield  is  from  95  to  100  g.,  or  33%,  based  upon  the  carbon  tetrachloride  used.  After 
recrystallization  from  glacial  acetic  acid,  the  substance  melts  at  295-300°  with  the  evolu- 
tion of  phenol. 

Anal.     Calcd.  for  Ci9Hi4Oj:  C,  78.59;  H,  4.86.     Found:  C,  78.20;  H,  4.94. 

Pure  aurin  changes  from  yellow  to  red  between  PH  5.6  and  6.5. 
Combination  with  Solvents  of  Crystallization. — Aurin  is  soluble  to 
the  extent  of  about  2  g.  in  100  cc.  of  boiling  glacial  acetic  acid  and  crys- 
tallizes from  the  solution  in  garnet-red  crystals.  When  benzene  is  added 
to  a  cold,  saturated  solution  of  aurin  in  glacial  acetic  acid,  the  dye  pre- 
cipitates on  long  standing  in  large,  heavy,  needle-like  crystals  with  steel- 
blue  reflection,  which  carry  acetic  acid  and  benzene.  In  acetic  acid, 
varying  in  concentration  from  80%  to  95%,  aurin  is  soluble  to  the  extent 
of  about  4  g.  in  100  cc.  at  the  boiling  temperature.  It  crystallizes  from 
this  solution  on  long  standing,  carrying  acetic  acid  and  water.  Aurin  is 
soluble  with  difficulty  in  acetone  and  in  methylethyl  ketone  and  it  crys- 
tallizes from  these,  carrying  solvent  of  crystallization.  As  previously 
mentioned,  aurin  takes  up  ether  of  crystallization  when  suspended  in  the 
moist  solvent. 

The  compositions  of  these  combinations  have  been  found  to  be  as  follows : 
from  acetic  acid  and  benzene,  2(Ci9Hi4O3).2(C2H4O2).C6H6;  from  acetic 
acid  and  water,  CigHuOa.lV^^HUC^.H^O;  from  acetone,  2(CigHi4O3).- 
3(C3H6O) ;  from  methylethyl  ketone,  Ci9Hi4O3.C4H8O ;  from  ether,  C19H14O3.- 
C4Hi0O. 

AURIN  HYDROCHIXJRIDE. — Dale  and  Schorlemmer7  have  noted  the  tendency  of  aurin 
to  unite  with  acids  and  have  described  a  crystalline  product  of  aurin  with  one  molecule 
of  hydrogen  chloride.  This  property  of  fuchsones  to  unite  with  hydrogen  chloride  is 
well  known,  and  is  interpretated  by  some  as  formation  of  oxonium  and  by  others  as  that 
of  quinocarbonium  salts.  Gomberg8  assigned  to  the  addition  product  of  hydrogen  chlor- 

/==\  /OH. 
ide  with  aurin  the  constitution  (HOC6H4)2=C=\  /\ 

\=/\C1 

We  found  that  when  aurin  is  crystallized  from  alcohol  saturated  with  hydrogen 
chloride,  the  hydrochloride  precipitated  with  one  molecule  of  alcohol  of  crystallization, 
and  not  in  the  ratio  of  two  molecules  of  the  former  to  three  of  the  latter,  as  described  by 
Dale  and  Schorlemmer. 

Anal.     Calcd.  for  Ci9Hi5O3Cl.C2H6O:   C2H6O,  12.35.     Found:   12.3. 

The  compound  prepared  in  acetic  acid  as  the  solvent  contains  two  molecules  of 
acetic  acid  of  crystallization,  which  is  readily  driven  out  when  the  salt  is  heated  at  100° . 

Anal.     Calcd.  for  Ci9Hi6O3Cl:   HC1,  11.8.     Found:    11.5. 

Aurin  was  recrystallized  from  hot,  dil.  hydrochloric  acid  (1: 1).     It  precipitated  in 

7  Dale  and  Schorlemmer,  J.  Chem.  Soc.,  35,  154  (1879). 

8  Gomberg  and  Cone,  Ann.,  376,  213  (1910). 


11 

fine,  brown  needles;  these  were  washed  with  a  few  cubic  centimeters  of  water,  pressed 
on  a  porous  plate,  allowed  to  stand  for  24  hours,  powdered  and  air-dried  for  several  hours. 
When  heated  to  constant  weight  at  120°,  the  substance  lost  10.7%  of  water,  while  only  a 
trace  of  hydrogen  chloride  was  given  off.  The  composition  of  the  hydrate  is,  Ci»Hu- 
O3C1.2H2O. 

When  aurin  is  placed  even  in  dilute  solutions  of  hydrochloric  acid,  it  forms  an  addi- 
tive product  with  the  acid;  for  this  reason  hydrochloric  acid  must  be  avoided  in  precipi- 
tating aurin  from  its  alkaline  solutions.  The  avidity  with  which  aurin  unites  with 
hydrogen  chloride  in  dilute  aqueous  solutions  is  shown  by  the  following  experiment. 
Two  g.  of  pure  aurin  was  kept  at  50°  with  50  cc.  of  2%  hydrochloric  acid.  The  garnet- 
red  crystals  of  aurin  soon  turned  to  brown  threads  and  the  product  consisted  almost  en- 
tirely of  the  hydrated  aurin  hydrochloride. 

The  Possible  Existence  of  the  Quinoid  Carbinol  of  Aurin, 

(HOC6H4)2C 

In  previous  publications  from  this  Laboratory  it  has  been  shown  that  p- 
hydroxy-triaryl  carbinols  exhibit  the  phenomenon  of  tautomerism. 


OH  ;=±  R,=C= 
HO 

A  detailed  study  of  aurin  has  now  shown  that  it,  too,  in  all  probability 
exists  not  only  as  the  well-known  anhydride,  the  fuchsone,  but  also  as  an 
unstable  carbinol.  The  equilibrium,  however,  in  this  instance  is  wholly 
in  favor  of  the  quinonoid  tautomer,  which  is  not  surprising,  in  view  of  the 
three  hydroxyl  groups  in  the  molecule.  We  have  prepared  a  compound 
corresponding  in  composition  to  the  carbinol  plus  one  molecule  of  water 
of  crystallization.  From  a  consideration  of  the  following  points  it  appears 
that  we  have  here  not  a  dihydrate  of  aurin  but  actually  a  monohydrate  of 
the  carbinol:  (1)  there  is  a  decided  change  in  color  of  the  carbinol  from 
that  of  the  fuchsone  aurin;  (2)  aurin  hydrochloride,  which  possesses  a 
constitution  similar  to  our  surmised  carbinol,  also  contains  water  of  crys- 
tallization; (3)  one  molecule  of  water  in  our  carbinol  plays  a  different  role 
from  the  other,  the  first  being  given  off  more  readily  than  the  second. 

Ordinarily,  from  its  solutions  in  alkalies,  aurin  is  precipitated  as  the 
fuchsone,  whether  the  alkali  be  dilute  or  concentrated,  cold  or  hot,  whether 
the  precipitation  be  accomplished  by  just  neutralizing  with  acetic  acid, 
or  adding  an  excess  of  the  latter,  or  whether  the  dye  be  precipitated  by 
passing  carbon  dioxide  into  the  solution.  When  hydrochloric  acid  is 
used,  then  if  the  amount  of  acid  added  is  just  enough  to  neutralize  the  al- 
kali, fuchsone  is  the  result;  when  a  considerable  excess  of  acid  is  added, 
the  fuchsone  is  contaminated  with  some  fuchsone  hydrochloride.  We 
have  finally  succeeded  in  getting  the  desired  hydrated  carbinol  by  observ- 
ing the  following  conditions.  Aurin  is  dissolved  in  sodium  hydroxide  and 
to  the  warm  solution  (60°  to  70°)  is  slowly  added  dilute  (1:4)  hydro- 
chloric acid,  while  the  solution  is  well  stirred.  At  the  neutral  point,  the 


12 

precipitate  consists  of  light  red  fuchsone,  but  when  a  slight  excess  of  acid 
is  added  and  the  stirring  of  the  warm  solution  is  continued  for  15  minutes, 
the  red  fuchsone  soon  turns  to  fine  purple  threads  consisting  almost 
entirely  of  hydrated  aurin.  A  sample  of  such  a  product  was  dried  on  a 
porous  plate  for  24  hours,  powdered  and  air-dried  for  several  hours  longer. 
A  weighed  amount  of  the  substance  was  then  dehydrated  by  pass- 
ing over  the  sample  in  a  porcelain  boat  dry  air  at  room  temperature  and 
finally  heating  to  100°.  A  gradual  loss  of  water  occurred  —  1  mol.  in 
the  first  ten  hours,  0.8  mol.  in  the  next  40  hours,  and  evidently  approach- 
ing asymptotically  1.95  molecule  of  water. 

The  slight  excess  of  hydrochloric  acid  over  that  necessary  for  the  neu- 
tralization of  the  alkali  in  the  preparation  of  aurin  hydrate  probably  forms 
a  correspondingly  small  amount  of  aurin  hydrochloride.  This  gradually 
becomes  hydrolyzed  to  aurin  hydroxide  and  the  liberated  acid  continues 
to  act  in  the  same  manner  as  before  until  all  of  the  aurin  is  changed  to  the 
carbinol.  In  confirmation  of  this  interpretation  we  may  cite  the  fact  that 
pure  aurin  hydrochloride  when  suspended  in  water  is  transformed  to  the 
extent  of  50%  to  the  hydrated  fuchsone.  On  prolonged  standing,  espe- 
cially at  low  temperature,  fuchsone  is  the  product. 

Tri-acetyl-aurin  (Tri-/>-acetoxy-triphenylcarbinol),  (CHsCOOCgH^COH.—  Ten  g. 
of  aurin,  50  cc.  of  acetic  anhydride  and  2  g.  of  anhydrous  sodium  acetate  were  boiled 
under  a  reflux  condenser  for  two  hours.  The  yield  of  the  crude  product  was  14  g.,  that  is, 
almost  quantitative.  One  recrystallization  from  alcohol  gave  13  g.  of  a  colorless  crys- 
talline product;  m.  p.,  170-172°.  The  pure  compound  melts  at  172-173°.' 

Herzig10  describes  two  compounds  from  the  reaction  between  acetic  anhydride  and 
aurin,  one  insoluble  in  alcohol,  melting  at  172°;  the  other,  a  more  soluble  product,  melt- 
ing at  146-148°.  His  results  could  not  be  verified;  a  single  product  with  a  definite  melt- 
ing point  of  172-173°  was  obtained  by  us. 

TRI-ACETYL-AURIN  CHLORIDE  (TRI-/>-  ACETOXYTRIPHENYL  -  CHLOROMETHANE), 
(CH3COOC6H4)sCCl.  —  To  a  solution  of  15  g.  of  acetyl  aurin  in  10  cc.  of  hot  benzene  is 
added  8  cc.  of  acetyl  chloride.  The  solution  soon  turns  pink  and  on  longer  standing 
the  chloride  separates  in  well-formed,  slightly  colored  crystals  which  carry  benzene 
of  crystallization  in  the  ratio  of  one  molecule  of  benzene  to  one  molecule  of  the  chloride. 
When  the  compound  is  digested  with  absolute  ether,  it  still  retains  most  of  the  benzene. 
The  chloride  can,  however,  be  obtained  free  from  solvent  when  the  fine  crystalline  prod- 
uct is  heated  at  78°,  under  reduced  pressure,  in  a  stream  of  air  dried  over  phosphorus 
pentoxide.  The  compound  turns  yellow  when  heated,  begins  to  soften  at  168°  and  melts 
at  174°  to  a  red  liquid  with  the  evolution  of  acetyl  chloride. 

Anal.     Calcd.  for  C25H21O6C1:   Cl,  7.84.     Found:  7.76. 

The  chloride  begins  to  give  off  acetyl  chloride  at  120°,  more  rapidly  at  160°,  until 
one  molecule  of  acetyl  chloride  has  been  lost.  The  product  left  is  undoubtedly  diacetyl- 
aurin,  (CHsCOOCsH^C  :C6H4  :0. 

TRI-ACETYL-AURIN  PEROXIDE  (TRI  -p-  ACETOXYTRIPHENYL  -  METHYL  PEROXIDE), 

s.—  By  the  action  of  molecular  silver  upon  the 


9  (a)  Graebe  and  Caro,  Ber.,  11,  1122  (1878).     (b)  Dale  and  Schorlemmer,  Ann., 
196,  84  (1879).     (c)  Zulkowsky,  Ann.,  202,  191  (1880). 

10  Herzig,  Monatsh.,  17,  191  (1896). 


13 

chloride,  tri-/>-acetoxytriphenylmethyl  should  result.  This  free  radical  is  very  unstable 
and  was  not  isolated.  The  fact  of  its  transitory  existence  was  established  by  the  isola- 
tion of  the  corresponding  peroxide.  Quantitative  determinations  of  the  amount  of 
oxygen  that  is  absorbed  by  the  free  radical  were  made  by  sealing  the  chloride  and  silver 
with  a  solvent,  in  a  test-tube,  shaking  at  room  temperature  for  a  definite  time,  and  then 
measuring  the  amount  of  oxygen  that  the  solution  absorbs.  Results  were  obtained 
indicating  an  absorption  from  15  to  35%  of  that  calculated,  and  then  only  a  small  amount 
of  the  peroxide  could  be  isolated  from  the  solution  —  thus  indicating  the  progressive 
decomposition  of  the  radical;  but  by  shaking  a  bromobenzene  solution  of  the  chloride 
with  silver  directly  in  the  absorption  apparatus  in  the  presence  of  oxygen,  amounts  of 
absorption  were  obtained  varying  from  99%  to  103%  of  that  calculated,  and  then  the 
yields  of  peroxide  were  80  to  85%.  The  peroxide  was  recrystallized  from  methylethyl 
ketone.  It  melts  at  184-185°  to  a  red  liquid. 

Anal.     Calcd.  for  CtoHaOu:  C,  69.27;  H,  4.88.     Found:  C,  69.25;  H,  4.88. 

Tribenzoyl-aurin  (Tri-/>-benzoxytriphenylcarbinol),  (CeHUCOOCeHOaCOH.—  To 
10  g.  of  aurin  suspended  in  25  cc.  of  dimethylaniline  was  added  slowly  25  g.  of  benzoyl 
chloride  and  the  solution  was  finally  heated  to  60°  for  one  hour.  The  resulting  mixture 
was  washed  first  with  dil.  hydrochloric  acid  and  then  with  sodium  hydroxide.  The  yield 
after  one  recrystallization  of  the  crude  material  from  benzene  was  13  g.  of  pure  white 
product.  The  compound  melts  at  190-191°. 

Anal.     Gated,  for  C^HzsOr:  C,  77.40  ;H,  4.55.     Found:  C,  77.24;  H,  4.44. 

This  substance  surpasses  even  aurin  itself  in  the  singular  property  of  combining 
generally  with  solvents  from  which  it  is  crystallized.  It  is  difficult  to  find  an  explanation 
why  this  carbinol,  structurally  saturated,  should  possess  even  more  residual  affinity 
than  aurin,  which  is  structurally  unsaturated.  The  following  combinations  have  been 
obtained. 

Solvent  Product  Solvent  Product 

Benzene  2  CjoH^CVSCeHe  Acetone  C^HjsOy.CsHeO 

Acetic  acid  C4oH28O7.C2H4O2  Methylethyl  ketone      2  C40H28C>7.CH.,COC2HS 

Alcohol  C4oH28O7.C2H6O  Methylpropyl  ketone   2 
Carbon  tetrachloride 


TRIBENZOYL  -  AURIN  CHLORIDE  (TRI  -  p  -  BENZOXYTRIPHENYL  -  CHLOROMETHANE)  , 
(C6H5COOCcH4)3CCl.  —  To  a  solution  of  10  g.  of  tribenzoyl  aurin  in  75  cc.  of  warm 
benzene  was  added  calcium  chloride  and  the  solution  saturated  with  dry  hydrogen 
chloride.  After  several  hours  the  mixture  was  warmed  gently  in  order  to  bring  into  solu- 
tion the  carbinol  chloride  which  had  precipitated,  and  the  calcium  chloride  was  filtered 
off.  The  solution  was  concentrated  and  absolute  ether  added.  The  chloride  precipi- 
tated in  white  crystals  carrying  benzene  of  crystallization,  1  molecule  of  the  solvent  to  1 
of  the  chloride.  It  loses  the  solvent  of  crystallization  when  heated  to  temperatures 
slightly  above  the  boiling  point  of  benzene  and  melts  at  172-174°  to  a  red  liquid. 

Anal.     Calcd.  for  C4oH27O6Cl:  Cl,  5.56.     Found:  5.47. 

TRIBENZOYI-AURIN  PEROXIDE  (TRI-£-BENZOXYTRIPHENYL-METHYL  PEROXIDE), 
(CeHsCO.OCel^siC.O.O.CCCel^O.OCCeHsV—  As  in  the  case  of  the  acetyl  compound, 
it  is  necessary  to  prepare  this  peroxide  by  the  simultaneous  action  of  silver  and  oxygen 
upon  the  chloride  in  solution;  otherwise,  the  radical  decomposes  to  a  large  extent  prior 
to  the  oxidation  process.  By  the  simultaneous  action  of  silver  and  oxygen  upon  the 
solution  of  the  chloride,  absorptions  of  oxygen  were  obtained  varying  from  100%  to 
103%  of  that  calculated.  The  solution  of  the  peroxide  was  evaporated  to  a  small 
volume,  and  the  resulting  yellow  oil  was  treated  with  ether  which  dissolved  the  im- 


14 

purities,  while  the  peroxide  separated  as  colorless  crystals;  yield,  68%.  When  crystal- 
lized from  chloroform  it  carries  solvent  of  crystallization  which  it  retains  very  firmly. 
After  drying  at  100°  the  compound  when  further  heated  melts  at  218°  to  a  red  liquid. 

Anal.  Calcd.  for  CsoHwOu^CHCls:  C,  77.54;  H,  4.39;  CHC13(  27.85.  Found:  C, 
77.12,  77.06;  H,  4.34,  4.53;  CHCU,  27.3. 

Decomposition  of  Aurin  by  Air  and  Alkali. — Aurin  can  be  oxidized  by  atmospheric 
oxygen  in  the  presence  of  alkalies  with  much  greater  ease  than  has  been  usually  assumed. 
Fusion  is  not  necessary.11  Ten  g.  of  aurin  was  dissolved  in  200  cc.  of  5%  sodium  hy- 
droxide and  air  was  passed  through  the  cold  solution  for  72  hours.  The  filtered  solution 
gave,  on  the  addition  of  acetic  acid,  5.8  g.  of  pure  di-£-hydroxybenzophenone. 

Isolation  of  Leuco-aurin  from  the  Condensation  Product. — The  origin  of  this  prod- 
uct in  the  reaction  mixture  has  been  explained  on  p.  6  under  Section  5.  It  is  to 
be  found  in  the  ether  extract  of  that  fraction  of  the  mixture  which  is  insoluble  in  dil. 
ammonium  hydroxide.  The  moist  ether  extract  is  saturated  with  hydrogen  chloride, 
decanted  from  the  resulting  precipitate  and  evaporated  to  dryness.  The  residue  ob- 
tained on  the  evaporation  of  ether  consists  of  leuco-aurin  mixed  with  a  small  amount 
of  substance  (Z)  which  still  remains  unidentified.  The  leuco  compound  is  purified  by 
recrystallization  from  chloroform  and  benzene,  in  which  mixture  the  product  (Z)  is  more 
soluble  than  the  former. 

The  leuco  compound  was  identified  by  analysis  and  by  a  comparison  of  it  with 
leuco-aurin  which  was  prepared  directly  from  pure  aurin  by  reduction  with  zinc  dust 
and  acetic  acid.12  Each  sample  softened  at  235°  and  melted  at  240°.  Furthermore, 
each  of  the  two  samples  was  acetylated,  and  they  gave  the  identical  triacetyl-leuco- 
aurin;13  m.  p.,  135-137°. 

0,/>'p*-Trihydroxy-triphenyl  Carbinol  (X) 

Isolation  from  the  Condensation  Mixture. — As  mentioned  in  the  preceding  para- 
graph, this  compound  is  to  be  found  together  with  leuco-aurin.  When  the  ether  extract 
that  contains  these  two  substances  is  saturated  with  hydrogen  chloride,  the  o,  p',  p"- 
trihydroxy  carbinol  forms  an  insoluble  carbinol-chloride,  which  on  treatment  with  alkali 
gives  the  carbinol,  or  its  anhydride  the  fuchsone.  This,  however,  contains  some  im- 
purity which  is  not  easily  separated.  Freshly  precipitated,  the  almost  colorless  carbinol 
changes  rapidly  to  a  red  powder  which  is  soluble  in  ether;  when  the  product  is  dried, 
it  is  rendered  insoluble  in  ether.  We  have  failed  to  obtain  the  carbinol  in  crystalline 
form  to  be  identified  directly  as  such.  Methylation,  benzoylation  and  acetylation  also 
failed  to  give  rise  to  products  that  could  be  crystallized.  We  then  reduced  our  crude 
carbinol  with  zinc  and  acetic  acid  to  the  corresponding  leuco  base,  and  after  preliminary 
purification  of  it  from  benzene  and  petroleum  ether,  we  methylated  it  by  means  of  di- 
methyl sulfate.  The  resulting  substance,  m.  p.  113-114°,  proved  identical  with  o,p',- 
p"-trimethoxy-triphenylm  ethane  which  was  prepared  from  its  corresponding  carbinol 
that  had  been  synthesized  by  the  Grignard  reaction. 

Preparation  of  0,/>',£*-Trimethoxy-triphenyl  Carbinol  by  the  Grignard  Reaction. — 
The  Grignard  reagent  was  prepared  from  o-iodo-anisole  in  ether.  Di-/>-methoxy- 
benzophenone  was  then  added  and  after  the  mixture  had  been  boiled  for  a  short  time, 
benzene  was  added,  the  ether  distilled  and  the  boiling  continued.  The  insoluble  mag- 
nesium compound  of  the  earbinol  was  filtered  off,  washed  with  benzene,  and  decomposed 


11  (a)  Caro  and  Graebe,  Ber.,  11,  1348  (1878).     (b)  Dale  and  Schorlemmer,  Ann., 
217,  388  (1883).     (c)  Baeyer  and  Burkhart,  Ann.,  202,  126  (1880). 

12  Dale  and  Schorlemmer,  J.  Chem.  Soc.,  26,  439  (1873). 

13  (a)  Ref.  9  a,  p.  1117.     (b)  Herzig  and  Smoluchowski,  Monatsh.,  15,  80  (1894). 


15 

in  the  usual  manner.     The  carbinol,  recrystallized  from  benzene  and  petroleum  ether, 
melted  at  124-125°. 

0,£',£*-Trimethoxy-tripheiiylmethane. — This  was  prepared  from  the  carbinol 
described  by  reduction  with  zinc  dust  at  80°.  The  product  was  recrystallized  from 
petroleum  ether.  It  melted,  like  the  methane  from  the  carbinol  in  the  condensation 
mixture,  at  113-114°.  A  mixture  of  the  two  methane  samples,  which  came  from  the 
two  different  sources,  also  melted  at  113-114°. 

p-Hydroxyphenyl-xanthane  (XVI) 

This  product,  in  the  scheme  employed  for  the  separation  of  reaction  products,  comes 
in  the  fraction  together  with  diphenyl  carbonate;  both  are  soluble  in  ether  and  insoluble  in 
cold  dil.  sodium  hydroxide  solution;  the  latter,  however,  does  not  react  with  alkali,  while 
the  former  gives  a  sodium  salt  that  is  insoluble  in  cold,  but  soluble  in  hot  alkali.  The 
separation  of  the  two  is  therefore  readily  accomplished.  The  xanthane  was  recrys- 
tallized from  ether  and  petroleum  ether  and  melted  at  148°  to  150°  with  decomposition. 

Anal.     Calcd.  for  Ci9H14O2:  C,  83.19;  H,  5.15.     Found:  C,  83.18;  H,  5.17. 

^-Methoxyphenyl-xanthane. — For  further  identification  our  hydroxy-xanthane 
was  methylated  by  means  of  dimethyl  sulfate  and  the  methoxy  derivative  compared 
with  £-methoxyphenyl-xanthane  obtained  directly  from  the  corresponding  xanthenol14 
by  reduction  with  zinc  dust.  The  two  proved  identical,  each  sample  of  the  xanthane 
melting  at  112-113°. 

/>-Hydroxyphenyl-fluorone  (XIV) 

Isolation. — This  product  constitutes  about  15%  of  the  whole  reaction  mixture  and, 
in  weight,  equals  one-fourth  of  the  aurin.  Unlike  the  latter,  it  is  not  soluble  in  dil. 
ammonium  hydroxide,  as  it  is  a  weaker  acid,  containing  only  one  phenolic  hydroxyl 
group  while  aurin  contains  two.  It  is  separated  from  other  products  as  indicated  on 
p.  8.  The  crude  fluorone  is  now  washed  with  50%  acetone,  which  removes  small 
amounts  present  of  0,/>',p"-trihydroxy-carbinol  (X)  and  of  a  greenish-black  substance, 
that  otherwise  interfere  with  the  crystallization  of  the  fluorone.  After  this  treatment 
the  product  is  a  light  orange  powder  and  is  quite  pure.  It  gives  with  alkali  a  red  color 
bordering  on  orange,  while  aurin  gives  a  pure  red  solution.  •  The  fluorone  is  insoluble  in 
the  usual  organic  solvents  except  acetic  acid,  from  which  it  crystallizes  in  orange-red 
crystals.  It  melts  at  285-295°  with  the  evolution  of  phenol. 

Anal.     Calcd.  for  Ci,H12O3:   C,  79.14;  H,  4.20.     Found:   C,  78.80;  H,  4.31. 

The  constitution  of  the  compound  described  above  as  />-hydroxyphenyl-fluorone 
has  been  established  (1)  by  determining,  through  acetylation,  the  number  of  hydroxyl 
groups  present  in  the  molecule;  (2)  by  comparison  of  the  monomethoxy-  and  dimethoxy- 
derivatives  of  our  condensation  product  with  the  similar  derivatives  of  />-hydroxyphenyl- 
fluorone  that  had  been  prepared  by  means  of  the  Grignard  reaction;  (3)  finally,  by 
comparing  the  product  with  the  compound  which  was  definitely  known,  from  the  manner 
of  its  synthesis,  to  possess  the  constitution  of  £-hydroxyphenyl-fluorone. 

^-Acetoxyphenyl-fluorone   and   £-Acetoxyphenyl-3-acetoxy-xanthenol. — 
C6H4O.COCH,  C6H4O.COCH, 

Q OH 

and        C6H4<^    Nc6H3O.COCH, 

To  5  g.  of  hydroxy-fluorone  was  added  50  cc.  of  acetic  anhydride  and  2  cc.  of  sulfuric 
acid,  care  being  taken  to  keep  the  solution  cold.  After  two  days,  the  mixture  was 
poured  into  water  and  the  precipitated  mass  was  washed  with  alkali  and  water.  The 

14  Gomberg  and  West,  J.  Am.  Chem.  Soc.,  34,  1538  (1912). 


dry,  yellow  product  was  allowed  to  stand  in  contact  with  ether,  whereupon  the  diacetyl 
derivative  dissolved.  The  mono-acetyl  compound  was  obtained  crystalline  and  pure 
from  its  concentrated  solution  in  benzene  by  adding  a  large  volume  of  ether.  It  melts 
at  204-205°.  The  diacetyl  compound  was  obtained  also  in  white  crystals  by  adding 
to  its  solution  in  benzene  a  large  volume  of  carbon  disulfide;  m.  p.,  138-140°. 

Anal.  Mono-acetyl  compound.  Calcd.  for  C21Hi4O4:  C,  76.34;  H,  4.27.  Found: 
C,  76.21;  H,  4.30. 

Diacetyl  compound.  Calcd.  for  CjsHigOe:  C,  70.75;  H,  4.64;  acetic  acid,  30.77. 
Found:  C,  70.40;  H,  4.65;  acetic  acid,  29.71. 

^-Methoxyphenyl-fluorone  and  p-Methoxyphenyl-3-methoxy-xanthenol. — 
C6H4OCHS  C6H4OCH3 

/°V  /C^-OH 

C6H4    <      >C6H3:O         and       C6H4<       >C6H3OCH, 

NX  NX 

When  hydroxyphenyl-fluorone  is  methylated  by  means  of  methyl  sulfate  it  takes 
up  one  or  two  methyl  groups,  depending  upon  the  conditions  of  the  experiment.  When 
the  methylation  is  carried  out  at  room  temperature  in  aqueous  4%  sodium  hydroxide 
solution>  methoxyphenyl-fluorone,  which  is  the  first  product  of  the  reaction,  precipitates 
and  consequently  further  action  of  methyl  sulfate  is  greatly  retarded.  However,  when 
50%  acetone  solution  is  employed,  the  methylation  proceeds  to  the  end  and  the  di- 
methoxy  derivative  is  the  result. 

The  monomethoxy  derivative  was  crystallized  from  benzene  and  from  acetone  and 
the  orange-colored  crystals  melted  at  206-208°. 

Anal.     Calcd.  for  C20H14O3:  C,  79.47;  H,  4.67.    Found:   C,  79.69;  H,  4.77. 

The  compound  described  proved  to  be  identical  in  every  way  with  the  p-methoxy- 
phenyl-fluorone  prepared  by  Grignard's  reaction  from  3-hydroxyxanthone15  and  p- 
anisylmagnesium  iodide. 

The  dimethoxy  derivative,  recrystallized  from  alcohol  and  then  from  benzene, 
melted  at  112-114°. 

Anal.     Calcd.  for  C2iH18O4:   C,  77.47;  H,  10.76.    Found:   C,  77.51;  H,  10.79. 

For  purposes  of  comparison  with  our  condensation  product,  the  same  dimethoxy 
compound  was  prepared  from  3-methoxyxanthone16  and  />-anisylmagnesium  iodide. 
This,  like  our  product  from  the  condensation  reaction,  melted  at  112-113°.  The  two 
on  treatment  with  acetyl  chloride  gave  identical,  colored  carbinolchloride-hydrochlorides 
melting  at  120-122°. 

Synthesis  of  />-Hydroxyphenyl-fluorone. — The  £-methoxyphenyl-fluorone,  pre- 
pared by  Grignard's  reaction  as  described  above,  was  demethylated  by  aluminum  chlor- 
ide in  antimony  trichloride  as  the  solvent.  After  purification,  the  product  proved  to 
be  identical  in  every  respect  with  the  compound  obtained  in  the  condensation  reaction. 
It  melted  at  285-295°  with  the  evolution  of  phenol. 

Oxidation  by  Air  and  Alkali. — A  solution  of  10  g.  of  />-hydroxyphenyl-fluorone  in 
100  cc.  of  5%  sodium  hydroxide  solution  was  warmed  on  the  steam-bath  for  12  hours. 
Upon  neutralization  of  the  solution,  6  g.  of  o,£'-dihydroxybenzephenone  separated. 
This  was  recrystallized  from  benzene  and  melted  then  at  150-151°.  Michael  gives  the 
melting  point  as  143-144°,  Pfeiffer  as  147-148°  and  Baeyer  as  150-152  °.17 

18  (a)  Baeyer,  Ann.,  372,  100  (1910).  (b)  Ullmann  and  Denzler,  Ber.,  39,  4335 
(1906). 

16  Ref.  15  a.     Ref.  14,  p.  1559. 

17  (a)  Michael,  Am.  Chem.  J.,  5,  83  (1883).     (b)  Pfeiffer,  Ann.,  398,  167  (1913). 
(c)  Baeyer,  Ann.,  354, 177  (1907). 


17 

For  further  identification,  the  ketone  was  acetylated  and  the  acetyl  derivative 
melted  at  89-90°,  while  Michael  gives  the  melting  point  as  84-85°,  and  Dimroth  and 
Zoeppritz  as  120V8 

This  may  be  considered  as  a  practical  method  for  the  preparation  of  0,/>'-dihydroxy- 
benzophenone,  since  the  fluorone  from  which  it  is  obtained  is  now  itself  readily  ac- 
cessible. 

The  Oxalic  Acid  Method  for  the  Preparation  of  Aurin 

By  following  the  procedure  as  given  by  Zulkowski,19  the  yield  of  the 
crude  reaction  product  was  about  40%,  based  upon  the  amount  of  phenol 
used.  The  crude  mixture  was  separated  into  its  components  according 
to  the  scheme  outlined  on  p.  201  of  this  paper.  The  results  are  given 
below  in  Col.  1;  parallel  with  these  figures,  hi  Col.  2,  are  reproduced 
Zulkowski's  data 

i  ii 

Aurin  85%  Aurin  55% 


Leuco-aurin 

Dihydroxybenzophenone 
p-Hydroxyphenyl-xanthane 
£-Hydroxyphenyl-fluorone 


15% 


"a-Aurin-oxide" 
" /3- Aurin-oxide" 
"Product  1" 
"Product  2" 


45% 


The  yield  of  pure  aurin  by  this  method  is  almost  exactly  the  same  as  that 
by  the  carbon  tetrachloride  'method,  namely,  about  31-33%  based  upon 
the  amount  of  phenol  used  hi  the  reaction.  Although  the  amount  of  by- 
products by  the  oxalic  acid  method  is  less  than  that  obtained  by  the 
carbon  tetrachloride  method,  the  former  method,  on  the  other  hand,  re- 
quires the  use  of  a  large  excess  of  oxalic  acid;  and  as  regards  the  by-prod- 
ucts in  the  second  method,  the  separation  of  pure  aurin  from  these  entails 
no  difficulty. 

The  Composition  of  Several  Technical  Samples  of  Aurin 

These  samples  were  obtained  from  various  sources  and  analyzed  as  to 
their  contents  according  to  our  scheme  of  separation.  In  addition  to  aurin, 
they  were  found  to  contain  leuco-aurin,  ^-hydroxyphenyl-fluorone,  p- 
hydroxyphenyl-xanthane,  di-£-hydroxybenzophenone  and  some  uniden- 
tified material.  The  material  from  the  Eastman  Kodak  Company 
(aurin)  contained  55%  of  aurin;  that  from  Merck  and  Company  (aurin) 
contained  44%;  that  from  the  Schuchardt  Chemical  Company  (corallin) 
contained  32%;  and  that  supplied  by  Grubler  and  Company  (corallin) 
contained  35%. 

This  investigation  was  made  with  the  assistance  of  the  National  Aniline 
and  Chemical  Company  Fellowship.  We  wish  to  express  our  obligations 
for  the  generous  aid  we  have  thus  received. 

18  (a)  Ref.  17  a,  p.  87.     (b)  Dimroth  and  Zoeppritz,  Ber.,  35,  992  (1902). 

19  Zulkowski,  Monatsh.,  16,  358  (1895). 


18  j; 

•»w 

Summary 

1.  The    condensation    reaction    between    carbon    tetrachloride    and 
phenol  has  been  investigated  in  detail.     Eight  of  the  nine  products  formed 
have  been  identified,  and  this  made  it  possible  to  give  an  interpretation 
as  to  the  mechanism  of  the  condensation  reaction. 

2.  Aurin  is  the  chief  product  formed.     Methods  have  been  worked 
out  for  obtaining  it  quite  pure,  and  a  number  of  new  derivatives  of  aurin 
have  been  prepared. 

3.  In  addition  to  aurin,  the  following  substances  were  isolated  from 
the  condensation  mixture:  leuco-aurin,  0,/?',£>'/-trihydroxytriphenyl  car- 
binol,     ^-hydroxyphenyl-fluorone,    ^-hydroxyphenyl-xanthane,    diphenyl 
carbonate,  di-^-hydroxybenzophenone  and  o,^'-dihydroxybenzophenone. 

4.  It  is  possible  to  alter  the  conditions  in  the  process  of  the  condensa- 
tion reaction  in  such  a  manner  that,  instead  of  aurin,  diphenyl  carbonate 
or  di-£-hydroxybenzophenone  becomes  the  chief  product  of  the  reaction. 
This  procedure  furnishes  excellent  preparative  methods  for  these  two 
substances.     The  decomposition  of  ^-hydroxyphenyl-fluorone  by  alkali 
and  air  furnishes  a  very  good  method  of  preparing  0,£>'-dihydroxybenzo- 
phenone. 

5.  Aurin  and  its  derivatives,   such  as  the  triacetyl  and  tribenzoyl 
carbinol,  possess  in  a  notable  degree  "residual  affinity,"  and  they  give  rise 
to  many  loosely  bound  combinations  with  alcohol,  ether,  ketones,  carbon 
tetrachloride,  aromatic  hydrocarbons,  etc. 

6.  It  was  found  that  the  method  hitherto  employed  for  making  aurin — 
namely,  from  phenol  and  oxalic  acid — gives  less  by-products  than  the 
carbon  tetrachloride  method,  but  furnishes  no  better  yields  and  is  wasteful 
because  it  requires  the  use  of  a  large  excess  of  oxalic  acid. 


i**-~  QT* /%***•*• 

OVEROOE. 

__—-== 


Photomount 
Pamphlet 

Binder 
Gaylord  Bros. 

Makers 
Syracuse,  N.  Y, 

PAT.  JAN  21,  1908 


10079 


578647 


A 


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